Direct drive for a wheel set

ABSTRACT

The invention relates to a drive for a wheel set ( 1 ) of a chassis, with the wheel set having two wheels ( 3 ) positioned on a wheel set shaft ( 2 ), which can be driven by at least one internal rotor motor that encompasses the wheel set shaft ( 2 ) and has a stator ( 10 ) and a rotor ( 19 ). This configuration provides a compact direct drive.

[0001] The invention relates to a drive for a wheel set of a chassis.

[0002] EP 0 413 337 A1 discloses an electromotive direct drive for arailway vehicle, having an electronically commutated electric motorplaced axially next to the wheel being driven and including a rotor,connected to the wheel being driven, for torque transmission. The rotorand the wheel being driven have rotation axes which are substantially inalignment. Moreover, the rotor is constructed as external rotor of theelectric motor in the absence of a housing of the electric motor and isprovided with permanent magnets distributed in ring-shaped fashion.Furthermore, the stator of the electric motor is restrained on thevehicle against execution of a rotation on a vehicle side which isdistal to the wheel being driven.

[0003] As consequence of its disposition and construction, there is thedrawback that this drive is hardly applicable for use in railwayvehicles with conventional wheel sets that are supported externally orinteriorly. The drive has to be shifted to the inside between bothwheels of the wheel set being driven, whereby the disk-likeconfiguration of this direct drive can be fitted in the available spacebetween both wheel only with great constructive difficulty. Thus, thisdrive is not suitable for propelling a wheel set with continuous shaft.

[0004] The invention is thus based on the object to provide a drive fora wheel set of a chassis, which requires less maintenance works and ismore cost-efficient to manufacture compared to conventional drivesystems. Moreover, this drive concept should have decreased energyconsumption and generate less noise emission. A further object of theinvention is the construction of this drive system so as to be useablealso in low-platform rail vehicles.

[0005] The posed object is attained by providing a drive for a wheel setof a chassis, including two wheels which are disposed on a shaft and canbe driven by at least one internal rotor motor which encompasses theshaft and has a stator and a rotor.

[0006] The term “chassis” is to be understood to include, i.a., bogiesand single axles.

[0007] Thus, the need for a transmission as well as for an elasticclutch between motor and wheel set is eliminated. A further advantage ofthis drive concept according to the invention is the reducedinstallation volume and the reduced weight of the overall drivearrangement compared to conventional drives.

[0008] According to a further configuration, the shaft of the wheel setis constructed as rotor at least along portions thereof. As a result,the shaft assumes electromagnetic as well as constructive functions. Onone hand, the shaft acts as rotor of the internal rotor motor andestablishes moreover as shaft the mechanical connection of both wheelsof the wheel set. As a consequence, the production costs of the driveare further decreased. Advantageously, the shaft is hereby configured ashollow steel shaft, resulting in a further reduction in weight of theoverall drive arrangement.

[0009] According to a particularly preferred embodiment, permanentmagnets are disposed on the shaft for electromagnetic interaction withthe stator of the internal rotor motor to thereby propel the wheel set.In particular advantageous is a direct bonding of the permanent magnetsupon the hollow steel shaft. Losses in the rotor are very low so thatthe yoke of the rotor does not necessarily be configured as a laminatedcore structure.

[0010] According to a further embodiment, the drive is configured aspermanent-excited synchronous motor. In order to equip the synchronousmotor with an increased torque density, the provision of a high polenumber, in particular greater than or equal to 16 poles, isadvantageous. This pole number, established as a consequence of theslight yoke height in view of the outer diameter of the giveninstallation space, leads to a fairly great air gap diameter. For thisreason, this drive as a result of this synchronous motor is alsoappropriate for the increasingly smaller wheel diameter that result inmore comfort in view of the lower floor height in the boarding zone anddoor area of railway vehicles.

[0011] The high pole number results also in very short winding endportions, thereby increasing the effectiveness of the synchronous motorand permitting a prolongation of the stack of laminations at setinstallation length of the drive. As a consequence, the synchronousmachine can be best suited to the existing, in particular tubularinstallation volume, in particular when small wheels are involved.

[0012] As the losses of the synchronous machine are encounteredsubstantially in the component at rest, i.e. in the stator in thepresent case, these losses should be dissipated through this region ofthe synchronous machine. The use of conventional self-ventilation andfan-cooled types is hereby conceivable. According to a furtherconfiguration of this invention, the stator has a liquid cooling, inparticular to prevent noise emission of the fan. Especially, when thestator has a casing of polygonal cross section, cooling ducts, requiredfor the liquid cooling, are arranged in the corners. Axial cooling ductsare essentially provided there in parallel relationship to the shaft ofthe wheel set. In particular, when the housing of the stator has atetragonal cross section, the outer diameter of the stack of laminationsis not decreased by the arrangement of these axial cooling ducts. As aresult of the near complete encapsulation of the synchronous machine bya housing with liquid cooling, in particular water cooling, and the lowrotation speed as well as the resultant elimination of an air cooler,very low noise emissions are achieved. As the rotation speed and theshaft diameter of wheel set and drive are identical, the bearing ofinternal rotor motor and wheel set can be combined, in particular whenthe wheel set is supported by an internal bearing. As a result, thenumber of required bearings is decreased to two rolling-contactbearings, just like in a non-driven wheel set. The production costs ofthe drive are thereby reduced as is the need for maintenance works. Inparticular, the need for re-lubrication is eliminated. In currentbearing technologies, the wheel set bearings have now longer servicelife than the wheel disks so that the provision of an external supportof the wheel sets, as considered appropriate in the past, becomes moot.

[0013] As the synchronous motor is supported upon the shaft of the wheelset, there is no longer any need for a complicated driving motorsuspension in the chassis. Rather, there is only a need for a torquesupport between drive and the vehicle. The hereby accompanying increaseof unsprung masses as a result of this drive according to the inventionis secondary as far as the stress upon the superstructure or the runningdynamics are concerned. In particular, the increase of the unsprungmasses in a speed range of up to 160 km/h is completely negligible.

[0014] Especially in the even higher speed range, it is advantageous todecouple the masses of the drive, at least partially, from the wheel setthrough suitable means, e.g. elastomers.

[0015] Hereby, rubber elements are, for example, arranged between rotorand shaft.

[0016] It is also possible to provide such a coupling between rotor andshaft, for example, in the area of the air gap.

[0017] Advantageously, this torque support includes at least a centralpush-pull rod arranged between the wheels of a wheel set. In this way,i.a. the tensile forces of the drive are transmitted directly to thevehicle. This results in a reduction of the pitching moments of thechassis. Moreover, a wheel set relief is avoided, when a tensile forceis applied, because the chassis is no longer exposed to any reactionmoments and forces of the drive. Moreover, there is no transmission ofdynamic reaction moments into the chassis, thereby reducing thetransmission of structure-borne noise.

[0018] Central arrangement of a push-pull rod as a simple torque supportis especially advantageous when the guidance of the wheel set inlongitudinal direction is hard because the tensile force is anywaytransmitted there via outer control arms.

[0019] When a soft longitudinal guidance of the wheel set is involved,the provision of a double push-pull rod is advantageous.

[0020] Furthermore, the drive and brake moments or the drive and brakeforces are no longer decisive when constructing the components, ratherit is only necessary to dimension with respect to the forces of thedriving dynamics.

[0021] This drive, applicable preferably for railway vehicles with wheelsets, introduces an economical drive concept for a direct drive forrailway vehicles and is appropriate also for small wheels with diametersof about 620 mm. The basic advantages such as smaller energyconsumption, less maintenance works, reduced production costs, smallernoise emissions, and prevention of oil losses of the transmission playan essential role hereby.

[0022] As wheel set and internal rotor motor are internally supported,the chassis can be provided much easier with a sound protection device.

[0023] The invention as well as further advantageous configurations ofthe invention according to the features of the subclaims will now bedescribed in more detail with reference to schematically illustratedexemplified embodiments in the drawing, in which:

[0024]FIG. 1 shows a side view of a principle illustration of a drivefor a wheel set,

[0025]FIG. 2 shows a longitudinal section of this wheel set,

[0026]FIG. 3 shows a cross section of this drive for the wheel set.

[0027] A wheel set 1 of a chassis, not shown in more detail in FIG. 1,includes a wheel set shaft 2 and the wheels 3 mounted to this wheel setshaft 2. The wheels 3 are secured to the wheel set shaft 2, inparticular shrunk-on. A rotor 19 of an electric motor configured asinternal rotor motor, in particular as synchronous motor, is disposedaccording to FIG. 2 upon the wheel set shaft 2. The rotor 19 hasessentially a tubular configuration and is situated on the wheel setshaft 2 between two steel plates 4. The tubular rotor 19 is hereby madepreferably as hollow steel shaft 5 supporting permanent magnets 6 aboutthe surface. Advantageously, the hollow steel shaft 5 is coupled viarubber elements 31 with the wheel set shaft 2. Stator 10 and the rotor19, which is situated upon the wheel set shaft 2, are mechanicallyconnected via rolling-contact bearings 7. These rolling-contact bearings7 assume the function wheel set bearing as well as the function drivingmotor bearing so that only two rolling-contact bearings 7 are to beprovided per wheel set 1. Supported in vertical direction by the housing11 of the stator 10 and the bearing of the rolling-contact bearings viaa primary spring assembly 8 are the longitudinal chassis beams, notshown in more detail. The drive of the wheel set 1 is guided via elasticcontrol arms 9 in longitudinal direction and for movements about itsvertical axis by the longitudinal chassis beams. The stator 10 of thedrive, configured as synchronous machine, includes a stack oflaminations, a housing 11 as well as windings disposed in slots 20 ofthe stator 10 to form winding end portions 12 on the respective endfaces of the stack of laminations. As a consequence of anelectromagnetic interaction of the stator 10 with its rotor 19 and therigid connection thereof with the wheel set shaft 2, the wheel set shaft2 rotates and thus the wheels 3 disposed on the respective ends of thewheel set shaft 2.

[0028]FIG. 3 is a cross section of a direct drive, designed inaccordance with the invention, for a wheel set 1, to depict the primaryspring assembly 8 upon the longitudinal chassis beams 30, thesubstantially square housing 11 of the stator 10 for lateral attachmentof a double tension rod 15 which receives the torque and thereby reducesat the same time the longitudinal connection in a central area so as todirectly transmit the torque into the vehicle body. The housing 11 ofthe stator 10 has cooling ducts 13 which are circulated in particular bya liquid to thereby assist in an efficient cooling of the stator 10.

[0029] The stack of laminations of the stator 10 exhibits the generallytypical slot-tooth geometry. In particular, the stack of laminations maybe provided with axial cooling ducts for circulation of, preferably,air. The rotor 19 of such a direct drive according to the invention ispositioned directly upon or about the wheel set shaft 2, with permanentmagnets 6 disposed on the side of the rotor 19, which side confronts theair gap 21. The permanent magnets 6 may be disposed as circular segmentlike structure upon the rotor 19 and in particular the hollow steelshaft 5, with the circular segments having a curvature substantiallycorresponding to the curvature of the rotor 19. The rotor 19 is thusconstructed to resemble a rotation-symmetric round rotor. Of course,other arrangements of permanent magnets 6 are possible as well, such as,e.g., secant-shape or V-shape. Also, the use of suitable measures, e.g.a bandage, enables a fixation of the permanent magnets 6 to the rotor,especially at high rotation speeds of the railway drives.

[0030] The direct drive of a wheel set 1 in accordance with theinvention enables a conceivably simple drive. Compared to conventionaldrives, there is neither a need for geared couplings nor for unnecessaryrolling-contact bearings 7 because only two greased integratedrolling-contact bearings are required for operation. As a result,maintenance work is significantly reduced. The wheel set direct driveaccording to the invention results in less energy costs and has a higherdriving efficiency. The suitability for small wheel diameters, asrepeatedly set forth, makes this direct drive also advantageous forlow-platform chassis and vehicle bodies.

1. Drive of a wheel set (1) of a chassis, having two wheels, which aredisposed on a wheel set shaft (2) and are driven by at least oneinternal rotor motor which encompasses the wheel set shaft (2) and has astator (10) and a rotor (19).
 2. Drive according to claim 1,characterized in that the wheel set shaft (2) of the wheel set (1) has alength configured at least along portions thereof as rotor (19). 3.Drive according to claim 2, characterized in that the wheel set shaft(2) is configured as hollow steel shaft.
 4. Drive according to one ofthe preceding claims, characterized in that the wheel set shaft (2) hasin the portion configured as rotor (19) permanent magnets (6) whichelectromagnetically interact with the stator (10) of the internal rotormotor to propel the wheel set (1).
 5. Drive according to claim 4,characterized in that the permanent magnets (6) are glued onto the wheelset shaft (2).
 6. Drive according to claim 4 or 5, characterized in thatthe drive is configured as permanent-excited synchronous motor.
 7. Driveaccording to claim 6, characterized in that the synchronous motor isconfigured with a large number of poles.
 8. Drive according to claim 7,characterized in that the pole number of the synchronous motor isgreater or equal
 16. 9. Drive according to one of the preceding claims,characterized in that at least the stator (10) of the internal rotormotor is cooled by liquid.
 10. Drive according to claim 9, characterizedin that the housing of the stator (10) has a polygonal cross section,with axial cooling ducts (13) provided in the corners.
 11. Driveaccording to one of the preceding claims, characterized in that twobearings (7) are provided for support of the wheel set (1) and of theinternal rotor motor.
 12. Drive according to one of the precedingclaims, characterized in that at least one central push-pull rod isprovided between the wheels (3) of a wheel set (1).
 13. Drive accordingto one or more of the preceding claims, characterized in that the massesof the drive, at least partially, are decoupled from the wheel set (1)by suitable means.
 14. Drive according to one or more of the precedingclaims, characterized in that the drive is applicable for railwayvehicles with wheel sets (1).
 15. Drive according to claim 14,characterized in that the railway vehicles include low-floor bogies.